It is well-known that the speed of an internal combustion engine output or crankshaft varies even during so-called steady-state operation of the engine, i.e. the shaft continuously accelerates and decelerates about the average speed of the shaft. The accelerations and decelerations are, of course for the most part, a result of power pulses from the engine cylinders. The pulses may be of uniform frequency and amplitude when cylinder charge density, air/fuel ratio, and ignition are uniform. However, such uniformity does not always occur, thereby producing pulses which vary substantially in frequency and amplitude. Whether uniform or not, the pulses, which are herein referred to as torsionals or torque fluctuations, are transmitted through vehicle drivelines and to passengers in vehicles. The torsionals, which manifest themselves as vibrations, are detrimental to drivelines and derogate passenger-ride quality. Further, when an engine is abruptly accelerated and/or decelerated by accelerator pedal movement or other factors, torque pulses ring through the driveline and also derogate ride quality.
A driveline may comprise a torque converter connected to the gearbox and lock-up clutch to selectively disconnect a turbine of the torque converter to the crankshaft. When the lock-up clutch is open, the impeller of the torque converter drives a turbine of the torque converter to generate an input torque for the gearbox that is higher than the torque from the internal combustion engine crankshaft. Furthermore, the drivetrain is assembled from the combination of sub-units or assemblies that are manufactured aside of the assembly line and delivered to the drivetrain manufacturer that assembles together the sub-units.